Toshiya Matsushima

Telencephalic and preoptic areas integrate sexual behavior in hime salmon (landlocked red salmon, Oncorhynchus nerka): results of electrical brain stimulation experiments

Various patterns of sexual behavior were evoked in freely swimming hime salmon by electrical stimulation of specific loci in the telencephalon and the preoptic area (POA) using chronically implanted electrodes. Furthermore, co-ordinated sexual behavior corresponding to stages of the natural spawning sequence was elicited from some of these brain regions. These results suggest that (1) sexual behavior is integrated in specific parts of the telencephalon and POA, and (2) within these regions there is a hierarchy of neural systems which mediate progressively more complete components of normal sexual behavior.

Apamin blocks the slow AHP in lamprey and delays termination of locomotor bursts

The effects of apamin on the slow afterhyperpolarization (sAHP) in spinal neurones and on the frequency of rhythmic bursting during fictive locomotion were investigated in the lamprey spinal cord in vitro. Apamin, which is a selective blocker of a small conductance KCa channel responsible for the sAHP in many types of neurones, was also found to reduce the sAHP in lamprey neurones. The summation of the sAHP is considered to be an important burst terminating factor in the spinal locomotor network and thereby to regulate the frequency of fictive locomotion. In support of this view, apamin was found to reduce the frequency of rhythmic bursting during fictive locomotion induced by kainate and NMDA. Serotonin, which has previously been shown to reduce the sAHP and slow the rate of rhythmic bursting, may therefore act, at least in part, on apamin-sensitive KCa channels.

The Mind Through Chick Eyes : Memory, Cognition and Anticipation

Abstract To understand the animal mind, we have to reconstruct how animals recognize the external world through their own eyes. For the reconstruction to be realistic, explanations must be made both in their proximate causes (brain mechanisms) as well as ultimate causes (evolutionary backgrounds). Here, we review recent advances in the behavioral, psychological, and system-neuroscience studies accomplished using the domestic chick as subjects. Diverse behavioral paradigms are compared (such as filial imprinting, sexual imprinting, one-trial passive avoidance learning, and reinforcement operant conditioning) in their behavioral characterizations (development, sensory and motor aspects of functions, fitness gains) and relevant brain mechanisms. We will stress that common brain regions are shared by these distinct paradigms, particularly those in the ventral telencephalic structures such as AIv (in the archistriatum) and LPO (in the medial striatum). Neuronal ensembles in these regions could code the chicks anticipation for forthcoming events, particularly the quality/quantity and the temporal proximity of rewards. Without the internal representation of the anticipated proximity in LPO, behavioral tolerance will be lost, and the chick makes impulsive choice for a less optimized option. Functional roles of these regions proved compatible with their anatomical counterparts in the mammalian brain, thus suggesting that the neural systems linking between the memorized past and the anticipated future have remained highly conservative through the evolution of the amniotic vertebrates during the last 300 million years. With the conservative nature in mind, research efforts should be oriented toward a unifying theory, which could explain behavioral deviations from optimized foraging, such as “naïve curiosity,” “contra-freeloading,” “Concorde fallacy,” and “altruism.”

Vibrational communication during spawning behavior in the himé salmon (landlocked red salmon,Oncorhynchus nerka)

SummarySexual behaviors of the salmon are composed of a stimulus-reaction chain, which ensures synchronous spawning between the sexes and successful fertilization. To characterize the signals involved in such a stimulusreaction chain, the body vibration and electromyographic activity of the trunk muscles during spawning were simultaneously recorded from freely behaving male and female pairs of himé salmon (landlocked red salmon,Oncorhynchus nerkd) and were analyzed in combination with a videographic analysis of behavior sequences. The results showed that the himé salmon have an elaborate communication system in which characteristic vibrational signals are exchanged. These are produced by body vibration due to trunk muscle activity related to spawning and are transmitted between the sexes with an accurate timing through the stimulus-reaction chain. They act as timing cues to synchronize gamete release and are thought to be shared among a wide variety of fishes. It was hypothesized that the lateral line sense is involved in the detection of these vibrational signals. Furthermore, based on the sequence matrix analysis as well as on information theory, intersexual behavioral sequences during spawning were analyzed statistically. The results showed that statistically significant interactions occur between the sexes and statistically significant amounts of information are transmitted through the interactions, supporting the results from recording experiments mentioned above. Characters of the signalling system and possible origins of the vibrational signals are also discussed.

Reward-related neuronal activities in basal ganglia of domestic chicks

We aimed to reveal what is coded in the basal ganglia of domestic chicks. In the water-reinforced ‘go’ task, chicks learned to peck selectively at a colored bead in order to obtain a drop of water. Out of 38 units obtained, seven showed excitatory activities specifically during the reward period. In the food-reinforced go/no-go task, chicks learned to discriminate two colors to obtain mash food after a delay period. They also learned to ignore another color, which was not associated with a reward. Out of 27 units obtained, four showed excitatory activities during the cue period, specifically when a food reward was anticipated. LPO neurons may code qualities of the obtained rewards, and also chicks anticipation of the forthcoming rewards.

Characterization of vibrational and visual signals which elicit spawning behavior in the male himé salmon (landlocked red salmon, Oncorhynchus nerka)

Himé salmon (landlocked red salmon, Oncorhynchus nerka) have an elaborate communication system, which ensures synchronous spawning by both sexes and successful fertilization. Both the vibrational and visual signals have been suggested to be involved in this communication system. To characterize these signals, vibrating or stationary three-dimensional models of various types were presented to the male, and male behavior elicited was examined. The results showed that the vibrating model mimicking certain aspects of the female behavior (‘prespawning act’) elicits the spawning in the male (Figs. 2, 3, 5). Furthermore, it was found that (1) the presence of both the vibrational and visual cues (Figs. 6, 7), and (2) spatial coincidence of these two cues (Fig. 8) are necessary for eliciting this behavior. Based on these results it was supposed that the vibrational and visual informations converge at the central nervous system where they are integrated to elicit the spawning.

The neurophysiological bases of undulatory locomotion in vertebrates

As a fish swims forwards, an, undulatory wave is transmitted along the body, pushing the animal forwards through the water. The underlying motor pattern consists of a consecutive activation of the muscle fibres in each segment along the body, forming an electromyographical travelling wave. The intersegemental coordination for both forward and backward swimming can be generated by neural circuitry in the brainstem-spinal cord and has already been identified experimentall. The evidence for two alternative hypotheses about the function of this circuitry is scrutinized.

Thyroid hormone determines the start of the sensitive period of imprinting and primes later learning

Filial imprinting in precocial birds is the process of forming a social attachment during a sensitive or critical period, restricted to the first few days after hatching. Imprinting is considered to be part of early learning to aid the survival of juveniles by securing maternal care. Here we show that the thyroid hormone 3,5,3′-triiodothyronine (T3) determines the start of the sensitive period. Imprinting training in chicks causes rapid inflow of T3, converted from circulating plasma thyroxine by Dio2, type 2 iodothyronine deiodinase, in brain vascular endothelial cells. The T3 thus initiates and extends the sensitive period to last more than 1 week via non-genomic mechanisms and primes subsequent learning. Even in non-imprinted chicks whose sensitive period has ended, exogenous T3 enables imprinting. Our findings indicate that T3 determines the start of the sensitive period for imprinting and has a critical role in later learning.

Neural correlates of the proximity and quantity of anticipated food rewards in the ventral striatum of domestic chicks

To identify the neuro‐cognitive substrates of valuation and choice, we analysed the neural correlates of anticipated food rewards in the ventral striatum of freely behaving chicks. One‐week‐old chicks were trained in a color‐discrimination task using four color cues (red, yellow, green and blue), each of which was associated with a different food reward. Choosing a red bead was immediately rewarded with a large amount of food, choosing a yellow bead resulted in an immediate‐small food reward, and choosing a green bead resulted in a late‐large food reward. We selected chicks that consistently chose a large and immediate food reward (red over yellow, and red over green), with the proximity of the food valued higher than the size of the food reward (yellow over green). Of the 47 neurons recorded from the ventral striatum of these chicks, 20 neurons selectively showed cue‐period responses to cues associated with food rewards. Five of these 20 neurons responded differentially during the cue period according to the expected delay to reward, and were thus assumed to code for the proximity of the reward. Additionally, three other neurons responded to the quantity of the reward. Furthermore, in the post‐operant delay period, many of these 20 neurons showed reward‐related activities that were linked to the proximity or presence of the food reward. We therefore propose that impulsive choice and behavioral perseveration observed after lesions of the ventral striatum could be due to impaired anticipation of rewards in the cue and delay periods, respectively.

The role of basal ganglia in reinforcement learning and imprinting in domestic chicks

Effects of bilateral kainate lesions of telencephalic basal ganglia (lobus parolfactorius, LPO) were examined in domestic chicks. In the imprinting paradigm, where chicks learned to selectively approach a moving object without any explicitly associated reward, both the pre- and post-training lesions were without effects. On the other hand, in the water-reinforced pecking task, pre-training lesions of LPO severely impaired immediate reinforcement as well as formation of the association memory. However, post-training LPO lesions did not cause amnesia, and chicks selectively pecked at the reinforced color. The LPO could thus be involved specifically in the evaluation of present rewards and the instantaneous reinforcement of pecking, but not in the execution of selective behavior based on a memorized color cue.